Tubular duct member

ABSTRACT

A tubular duct member comprises a plurality of sheet metal panels  10, 12  joined along adjacent longitudinal edges by cooperating folded sheet metal catches  14, 16,  the catches being pushed together such that respective detent surfaces  28, 30  on each catch engage behind one another to retain the edges of the sheets together. One of the catches  14  includes a body  36  of resilient material compressed between the catches and biasing the catches apart to maintain the detent surfaces  28, 30  bearing against one another.

This application is a Continuation of U.S. utility application Ser. No.12/857,733 filed Aug. 17, 2010, now U.S. Pat. No. 8,695,644, which is aContinuation-in-Part of PCT/EP2010/000433 filed Jan. 26, 2010, whichclaims priority to Irish national applications S2009/0132 andS2009/0133, both filed Feb. 18, 2009. The disclosures of theseapplications are incorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

This invention relates to a tubular duct member, i.e. a length of ductof which a number can be joined end to end to form tubular ducting for,e.g., air and gas distribution systems.

BACKGROUND

Typically, ducting is fabricated and assembled in a workshop. It is thenshipped to site, where it is combined with fittings such as reducers,T-pieces, bends, elbows, etc., to form air and gas distribution systems.

The disadvantages of the existing products are:

-   -   In the workshop fabrication process, a number of machines such        as guillotines, press brakes and seamers are used, together with        processes such as cutting and welding, making handling and        forming expensive.    -   Once made, storage, handling, road haulage and shipping costs        can be high, because of the significant volumes taken up by        large duct cross sections.    -   Offloading, storage and on-site handling to the point of        installation is also costly.

PRIOR ART

The following documents disclose lengths of duct manufactured by joiningindividual panels with male and female members that are “push-fitted”together:

1. JP 2003214692 A (FUKAGAWA) see FIGS. 1-3 and 8 in particular, andalso the English language abstracts.

2. JP 5172281 A (EE O Y SYST KENKYUSHO) see FIGS. 1-3 in particular, andalso the English language abstract.

3. JP 58006351 A (KAJIWARA) see FIG. 5 in particular, and also theEnglish language abstract.

4. US 2005/0109415 A1 (SNYDER) see whole document.

5. U.S. Pat. No. 2,847,034 (SWETT) see whole document

6. DE 1957274 A1 (BRINKMANN) see whole document, especially FIGS. 1-3.

7. EP 0071586 A1 (GRIMALDI) see whole document.

Documents 1 to 4 disclose the use of small projections for retainingmale members in female members to fix edges together.

Documents 1 to 3 in particular relate to ducting having a rectangularcross-section.

In document 5, the metal panels are resilient to a degree, so that thepanels are sealed with respect to each other when assembled. The panelsare joined by pushing a male member into a female member.

Document 6 (paragraph bridging pages 5 and 6) indicates that an adhesivemay or may not be used in the joint between the male and female members.

Document 7 discloses ducting formed from more than one panel, which arejoined by being joined by hooking one member within the other (andvice-versa). This document shows stacking to transport the individualparts to the site for assembly.

SUMMARY

In a first aspect the invention provides a tubular duct membercomprising a plurality of circumferential sheet metal panels joinedalong adjacent longitudinal edges by cooperating folded sheet metalcatches along each edge, the catches being pushed together such thatrespective detent surfaces on each catch engage behind one another toretain the edges of the sheets together, wherein at least one of thecatches includes a body of resilient material compressed between thecatches and biasing the catches apart to maintain the detent surfacesbearing against one another.

In a second aspect the invention provides a tubular duct membercomprising a plurality of circumferential sheet metal panels joinedalong adjacent longitudinal edges by cooperating folded sheet metalcatches along each edge, the catches being pushed together such thatrespective detent surfaces on each catch engage behind one another toretain the edges of the sheets together, wherein each catch comprises afolded metal rib of triangular cross-section, the detent surfaces beingsurfaces of said ribs, wherein a first catch comprises a first channelhaving opposite sidewalls with a first folded metal rib running alongthe inside of one sidewall of the first channel, and wherein the secondcatch comprises a second channel having opposite sidewalls with a secondfolded metal rib running along the outside of one sidewall of the secondchannel, the one sidewall of the second channel being inserted into thefirst channel so that the ribs engage behind one another and thesidewall of the first channel opposite the first folded rib beinginserted into the second channel.

In a third aspect the invention provides a method of making a ductmember comprising feeding sheet metal continuously from a roll,progressively folding the opposite edges of the sheet as it advances toform a respective folded metal catch along each edge, each catchincluding an upstanding wall defining with the main body of the sheet ashallow tray across the width of the sheet, dispensing a thermalinsulator in flowable form into the shallow tray as the sheet advancesso that the thermal insulator spreads out to fill substantially the fullwidth of the tray between the upstanding walls, the liquid thereaftersolidifying to form a solid thermally insulating layer, and cutting thesheet transversely into individual panels having a respective catchalong each edge for in-use push fit connection to a cooperating catchalong the edge of an adjacent panel.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view (not to scale) of a partially assembledduct member according to a first embodiment of the invention.

FIG. 2(a) is an end view of two sheet metal panels 10, 12 forming twoadjacent sides of the duct member of FIG. 1 about to be fitted together.

FIG. 2(b) is a cross section on line I-I of FIG. 2(a).

FIG. 2(c) is a cross section on line II-II of FIG. 2(a).

FIG. 3 shows a sheet metal blank from which the panel 10 of FIG. 1 isformed by folding. FIG. 3 also shows cross-sections of the folded panel10, corresponding to those shown in FIGS. 2(a) and (b), which identifywhere the regions of the blank end up in the folded panel.

FIG. 4 shows a sheet metal blank from which the panel 12 of FIG. 1 isformed by folding. FIG. 4 also shows cross-sections of the folded panel12, corresponding to those shown in FIGS. 2(a) and (c), which identifywhere the regions of the blank end up in the folded panel.

FIG. 5 shows a second embodiment of the invention employing insulatingpanels.

FIG. 6 shows a third embodiment of the invention.

FIG. 7 shows a variant of the embodiment of FIG. 5.

FIG. 8 shows a fourth embodiment of the invention.

FIG. 9 shows a further variant of the embodiment of FIG. 8.

FIG. 10 shows a further embodiment of the invention.

FIGS. 11 and 11(a) show detailed views of assembled ducting includingthe panels of FIG. 10.

DETAILED DESCRIPTION

Referring first to the embodiment shown in FIGS. 1 to 4, a tubular ductmember of substantially rectangular cross-section is assembled fromfirst and second pairs of opposite substantially flat sheet steel panels10, 10 and 12, 12 respectively. The panels 10 and 12 are joined alongadjacent longitudinal edges by cooperating catches 14 and 16 (in thepresent context “longitudinal” means in the direction of fluid flow inthe finished duct). The catches 14 are formed along opposite edges ofthe panels 10 by folding lateral extensions of a single sheet steelblank in the manner shown in FIG. 3, while the catches 16 are formedalong opposite edges of the panels 12 by folding lateral extensions of asingle sheet steel blank in the manner shown in FIG. 4. In FIGS. 3 and 4the lettered regions of the blanks correspond to the similarly letteredsections of the folded panel. The panels 10 and 12 also include foldedsheet steel end flanges 18 which are also formed from the blanks asshown. These end flanges allow individual duct members to be boltedtogether end to end to form a complete ducting system.

Each catch 16 comprises a narrow channel 20 with a folded metal rib 22of triangular cross-section running along the inside of one sidewall 21of the channel. Each catch 14 comprises a narrow channel 32 of which onesidewall comprises a flange 24 with a folded metal rib 26 of triangularcross-section running along the length of the free edge of the flange onthe outside of the channel 32. The adjacent edges of the panels 10 and12 are joined together by lining the rib 26 up with the channel 20 andpushing the panel 12 towards the panel 10, or vice versa, so that theflange 24 enters the channel 20. The wall 21 of the channel 20 bearingthe rib 22 is resiliently deflectable away from the opposite wall 34, sothat the rib 26 on the flange can pass by the rib 22 by deflection ofthe latter. As seen, each rib 22, 26 has its apex facing the other, tofacilitate the sliding engagement of the catches. When the catches arefully engaged the base 28 of the rib 26 snap-engages behind the base 30of the rib 22, the rib 22 returning to its undeflected position. Thusthe edges of the panels 10 and 12 are secured together. The edges of thepanels 10, 12 at the other three corners of the duct member are joinedin the same way.

At the same time as the flange 24 is slid into the channel 20 of thecatch 16 the wall 34 of the catch 16 slides into the channel 32. A bodyof resiliently compressible plastics material 36 is disposed along thebase of the channel 32, and this is compressed by the leading edge ofthe wall 34 when the catches 14, 16 are fully engaged. This both sealsthe join between the edges of the panels and biases the catches apart tomaintain the bases 28, 30 of the ribs 26, 22 strongly bearing againstone another to avoid a loose joint.

It will be appreciated that the triangular cross-section of the ribsprovides structural rigidity to the duct, both before and afterassembly. The compression seal 36 not only seals the joint but also forma key component of the mechanism locking the catches 14, 16 together.

In a further embodiment, FIG. 5, the duct member has a layer 38 ofthermally insulating lightweight solid foam material lining the insidesurface of the each panel 10, 12.

This foam can be glued in place or in an alternative implementation; thefoam can be sprayed on. In either case, it can be beneficial to provideretaining members to locate the foam within the panel. Thus, withreference to FIG. 7, it will be seen that the catches 16 of the panel 12readily provide such retaining members—although the foam 38′ in thiscase has a flat upper surface. In a variation of the panel 10′, thecatches 14′ are provided with two additional extension panels to provideretaining members 52. Thus, the foam can be located between either setof catches and glued in place as shown at 50; or sprayed into therespective wells provided by the catches.

In the foregoing embodiments the circumference of the duct member ismade up of four substantially flat steel panels, so that the duct memberhas a rectangular cross-section. In a further embodiment, FIG. 6, theduct member comprises two circumferential curved sheet steel panels 40joined edge to edge to form a duct member of rounded (i.e. circular orelliptical) cross-section. The catches 14, 16 may be constructed thesame as previously described, by folding at opposite edges of the steelpanels 40.

In the foregoing embodiments, each of the panels comprises either maleor female catches. However, in a fourth embodiment of the invention,each panel 80 includes a male catch 14′ at one edge and a female catch16′ at its opposite edge. While it will be seen from FIG. 8 that theribs 26′ and 22′ are equivalent to the ribs 26, 22 of the foregoingembodiments, instead of being folded back through right angled bends,each catch is formed by bending a flange 24′ back through one curve inthe case of catch 14′ and two curves in the case of catch 16′. A channel32′ with a rounded base is thereby formed in catch 14′ and is thusarranged to receive the curved wall 34′ of a catch 16′ formed in acounterpart panel (not shown).

Turning now to FIG. 9, where a further variant 90 of the panel of FIG. 8is shown. Here the triangular ribs 22″ and 26″ are formed by surfacescorresponding to only two sides of the triangle rather than all threesurfaces as in the previous embodiments. Also, the flange 24″ of catch16″ is bent once around a curve to form wall 34″ and then back through 2right angles 92 rather than around a second curve as in the panel ofFIG. 8.

Although not shown in FIGS. 8 and 9, a resilient member, as in theforegoing embodiments is included in the channel 32′,32″.

Finally, it will be noted that a step 82 is provided in the externalwall of catches 16′ and 16″ so that when they interlock with a catch14′, 14″ of a counterpart panel, the outer wall of channel 32′, 32″ liesflush with the outer surface of the panel 80/90.

It will be appreciated that when the embodiments of FIGS. 8 and 9 areimplemented in a generally curved panel as in FIG. 6, each of thecatches 14′, 16′ or 14″, 16″ will extend tangentially from the edges ofthe panel, rather than being bent with respect to the panel 80/90 as inthe case of the catch 14′ or 14″ of FIGS. 8 and 9.

It will also be appreciated that insulating material can be fitted tothe internal surface of the panels 80/90 as in the embodiments of FIGS.5 and 7, regardless of whether the panel is generally flat or curved.

FIG. 10 shows a further embodiment of the invention. FIG. 10(a) is anunderneath plan view of a duct panel 100, FIG. 10(b) is a cross-sectionon the line B-B of FIG. 10(a), and FIG. 10(c) is an enlargedcross-section similar to FIG. 10(b).

Like FIG. 8, the panel 100 has male and female catches respectivelyrunning along opposite parallel edges. These catches are constructed andoperate generally the same as the male and female catches 14′, 16′ ofFIG. 8 and, accordingly, the same reference numerals have been applied.The following description will concentrate on the differences from thepreceding embodiment, the basic operation of the catches being assumed.

The main difference is that each catch 14′, 16′ includes a respectiveupstanding wall 102, 104 formed by additional folding of the sheet metalat each edge of the panel through two 90 degree bends and one 180 degreebend, as shown in FIG. 10(c). These walls 102 and 104, together with themain body 106 of the panel 100 as a base, form a shallow tray across thewidth of the panel.

The panels 100 are produced continuously from a roll of sheet metal, theedges of the sheet being progressively folded as the sheet advances fromthe roll to form the catches 14′, 16′ and the upstanding walls 102, 104,the sheet then being cut transversely into individual panels. However,after the folding of the catches and the upstanding walls, but beforethe sheet is cut into individual panels, a liquid polyurethane (LPU) iscontinuously dispensed into the shallow tray formed by the walls 102,104 and the metal sheet. This flows sideways to fill the full width ofthe tray between the walls 102, 104 and rapidly cures (within minutes)to form a solid insulating layer 110. Longitudinal and transversestrengthening ribs 112 are formed in each panel by pressing before theapplication of the LPU. Finally, end flanges 118 as shown in theassembly drawing of FIG. 11 and the detailed view of FIG. 11(a), servingthe same purpose as the integral flanges 18 in FIGS. 1 to 4, are riveted(or alternatively spot welded) to the transverse cut ends of each panelfor fixing each panel to an adjacent panel.

In the preceding embodiments a hard polymer lining 114 is optionallysprayed onto the exposed surface of the foam/insulating layer 38 or 110,FIGS. 5 and 10. This has two advantages. First, it provides a hardenedsurface which serves to protect the underlying layer 38 or 110 when theducts are being cleaned. Second, although the layer 38 or 110 has acertain amount of flame resistance, it can still be flammable. The hardpolymer lining is a flame retardant, and provides a higher fireresistance than the underlying material. The hard polymer layer 114 hasa thickness of about 3 mm, in contrast with the layer 38 or 110 which istypically 32 mm thick. The flame retardant polymer 114 is preferably ofthe type produced by BASF under the mark Elastocoat C6325/105.

In embodiments of the invention where the assembled ducting, for exampleas shown in FIGS. 11 and 11(a), includes an insulating layer 110possibly coated with a polymer lining 114, a durable and relativelyimpervious internal lining is provided, by comparison with using forexample Rockwool or equivalent as an insulator either within or aroundthe ducting. This layer/lining does not accommodate rodents or harbouror promote the spread of bacteria, such as Legionella as readily asprior art systems. At the same time, the ducting can be transported inflat packed form and when assembled can provide a relatively airtightconduit for use in many applications.

Typical applications for the invention are in heating, ventilation,air-conditioning and refrigeration ducting.

Advantages of the invention are:

-   -   The component panels can be formed in high volume and at low        cost.    -   Joints are formed as an integral part of each panel during the        manufacturing process and so do not have to be made and fitted        separately.    -   The component panels that make up the assembly can be mass        produced and palletised automatically, protected and made ready        for shipping on an automated line. This results in low raw        material cost, labour cost and machining costs.    -   Overland haulage, shipping and airfreight costs are reduced,        since volume is reduced.    -   Storage, loading, unloading and handling at all stages along the        supply chain are facilitated by pre-palletising.    -   Panels can be landed and positioned close to the point of use.        Subsequently, when de-palletised, the panels can individually be        moved to the installation point and easily assembled there.

The invention is not limited to the embodiments described herein whichmay be modified or varied without departing from the scope of theinvention.

What is claimed is:
 1. A tubular duct member comprising a plurality ofcircumferential sheet material panels joined along adjacent longitudinaledges by cooperating sheet material catches formed along each edge, thecatches being pushed together such that respective detent surfaces oneach catch engage behind one another to retain the edges of the sheetstogether, wherein at least one of the catches includes a body ofresilient material compressed between the catches and biasing thecatches apart to maintain the detent surfaces bearing against oneanother, wherein each catch comprises a rib of triangular cross-sectionextending along the respective edge, the detent surfaces being surfacesof said ribs.
 2. A duct member as claimed in claim 1, wherein each catchcomprises a folded metal rib.
 3. A duct member as claimed in claim 1,wherein a first catch comprises a first channel having oppositesidewalls with a first rib running along the inside of one sidewall ofthe first channel, and the second catch comprises a flange with a secondrib running along its length, the flange being inserted into the firstchannel so that the ribs engage behind one another.
 4. A duct member asclaimed in claim 3, wherein the second catch comprises a second channelhaving opposite sidewalls with the second rib running along the outsideof one sidewall of the second channel, wherein the sidewall of the firstchannel opposite the first rib is inserted into the second channel, andwherein the body of resilient material is located at the base of thesecond channel for engagement by the sidewall of the first channelinserted therein.
 5. A duct member as claimed in claim 3, wherein theone sidewall of the first channel is resiliently deflectable away fromthe opposite wall to allow the first rib to pass by it when engaging thecatches.
 6. A duct member as claimed in claim 1, further including alayer of thermally insulating material lining the inside surfaces of thepanels.
 7. A duct member as claimed in claim 6, further including alayer of a flame retardant polymer on the layer of thermally insulatingmaterial.
 8. A duct member as claimed in claim 6, wherein the panels aresubstantially flat and the catches along the opposite edges of eachpanel each includes an upstanding wall defining with the main body ofthe panel a shallow tray across the width of the panel, the traycontaining a layer of a cured thermally insulating polymer.
 9. A ductmember as claimed in claim 1, wherein there are four substantially flatpanels joined edge to edge to form a duct member of substantiallyrectangular cross-section.
 10. A duct member as claimed in claim 1,wherein there are a plurality of curved panels joined edge to edge toform a duct member of rounded cross-section.